From: Philipp Stephani <p.stephani2@gmail.com>
To: eliz@gnu.org
Cc: Philipp Stephani <phst@google.com>, 35328@debbugs.gnu.org
Subject: bug#35328: [PATCH] Improve documentation around standard error pipes (Bug#35328).
Date: Sun, 21 Apr 2019 18:11:47 +0200 [thread overview]
Message-ID: <20190421161147.29403-1-phst@google.com> (raw)
In-Reply-To: <CAArVCkT+VQNasm+ALN1j6wHoJLqqEB969vD66Bi4rMymFsbN4A@mail.gmail.com>
* doc/lispref/processes.texi (Asynchronous Processes): Document
existence and properties of the standard error process.
(Accepting Output): Document that one has to accept output from the
standard error process separately.
---
doc/lispref/processes.texi | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi
index 7eb136af5f..3af8a1d5eb 100644
--- a/doc/lispref/processes.texi
+++ b/doc/lispref/processes.texi
@@ -701,6 +701,18 @@ Asynchronous Processes
@var{stderr} is @code{nil}, standard error is mixed with standard
output, and both are sent to @var{buffer} or @var{filter}.
+If @var{stderr} is a buffer, Emacs will create a pipe process, the
+@dfn{standard error process}. This process will have the default
+filter (@pxref{Filter Functions}), sentinel (@pxref{Sentinels}), and
+coding systems (@pxref{Default Coding Systems}). On the other hand,
+it will use @var{query-flag} as its query-on-exit flag (@pxref{Query
+Before Exit}). It will be associated with the @var{stderr} buffer
+(@pxref{Process Buffers}) and send its output (which is the standard
+error of the main process) there.
+
+If @var{stderr} is a pipe process, Emacs will use it as standard error
+process for the new process.
+
@item :file-handler @var{file-handler}
If @var{file-handler} is non-@code{nil}, then look for a file name
handler for the current buffer's @code{default-directory}, and invoke
@@ -1882,6 +1894,18 @@ Accepting Output
(while (accept-process-output process))
@end example
+If you have passed a non-@code{nil} @var{stderr} to
+@code{make-process}, it will have a standard error process.
+@xref{Asynchronous Processes}. In that case, waiting for process
+output from the main process doesn't wait for output from the standard
+error process. To make sure that you have received both standard
+output and error from a process, use the following code:
+
+@example
+(while (accept-process-output process))
+(while (accept-process-output stderr-process))
+@end example
+
@node Processes and Threads
@subsection Processes and Threads
@cindex processes, threads
--
2.20.1 (Apple Git-117)
next prev parent reply other threads:[~2019-04-21 16:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-19 19:36 bug#35328: 27.0.50; Lisp reference, "Accepting Output": Should describe what happens to standard error Philipp
2019-04-20 7:12 ` Eli Zaretskii
2019-04-21 13:58 ` Philipp Stephani
2019-04-21 16:11 ` Philipp Stephani [this message]
2019-04-22 9:25 ` bug#35328: [PATCH] Improve documentation around standard error pipes (Bug#35328) Eli Zaretskii
2019-04-22 14:08 ` Philipp Stephani
2019-04-21 19:12 ` bug#35328: 27.0.50; Lisp reference, "Accepting Output": Should describe what happens to standard error Eli Zaretskii
2019-04-22 9:14 ` Philipp Stephani
2019-04-22 9:26 ` Eli Zaretskii
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